Field of the Invention
The invention relates to an electric power transmission cable in particular for an overhead line.
It relates more specifically to an electric power transmission cable, in particular for an overhead electric power line, comprising at least one central composite core consisting of fibers impregnated by a matrix and the specific strength of which is greater than 0.4 MPa·m3/kg and at least one layer of mutually interlocking conductive wires, made of aluminum or of an aluminum alloy and wound around this core.
Description of the Related Art
Such a cable is described in patent document EP 1 816 654.
This electric power transmission cable, in particular for an overhead electric power line, comprises a central composite core consisting of fibers impregnated by an epoxy resin matrix and two layers of conductive wires of Z- and S-shaped cross section, made of aluminum or of aluminum alloy, wound around the core. Optionally, the core may be covered with a layer of insulating material.
Such conductive wires are shaped wires according to the standard IEC 62219.
Such a cable may comprise a single central core, as represented, or three central cores.
It may also comprise one or more lavers of conductive wires 3.
The operating temperature of such a cable may reach 200° C. or more. It therefore turns out, since all of the components of the cable are blocked at the ends by anchorages, that, during an increase in the temperature of the conductive wires, from ambient temperature to the operating temperature of the cable, the layers of conductive wire have a tendency to swell as a result of the difference in expansion coefficient of the core and of the conductive wires, and the conductive wires have a tendency to come out of their layer which may lead to a dislodgement of the wires out of their layer. It is even possible to observe the formation of a squirrel cage type positioning of the conductive wires which has a tendency to be reduced when the thermal stress has stopped.
It is to be feared that after a certain number of thermal cycles, one or more conductive wires do not return to their correct place within their layer and thus give rise to an increase in the corona effect and also an increase in noise nuisance.